1. Field of the Invention
This invention relates generally to fluid flow control devices and more particularly to a novel fluid valve.
2. Prior Art
The improved valve of this invention is intended for use as a vacuum relief valve in a vacuum system which must be vented to atmosphere under certain conditions. The valve has particular utility in industrial vacuum cleaning systems and for this reason will be described in this context. However, the valve may be used for any other purpose for which it is suitable.
Industrial vacuum cleaning systems are used to clean up a wide variety of debris from sewers, streets, railways, sludge ponds, waste collection areas, and a wide variety of other locations. The debris may be the result of a natural occurrence, such as a flood or hurricane, or the result of an accident such as a truck or rail tank car spill, or the result of deliberate action, and may range from solids, such as dirt, rocks, and other solid debris, through semi-liquids, such as sludge and mud, sometimes laden with solids, to liquids.
Simply stated, an industrial vacuum cleaning system comprises a vacuum or suction line in the form of a flexible hose having an intake end which is held by an operator, and a vacuum source, such as a high velocity blower, for producing high velocity air flow into the hose through its intake end and through the hose to a separator in which the debris is separated from the air. The air is discharge back to the atmosphere, and the debris is conveyed to a collection chamber. In use, the operator moves the intake end of suction hose back and forth over the debris to be vacuumed in such a way that the debris is sucked into the hose.
Industrial vacuum cleaning systems of this kind are commonly mounted on a truck so that they may be transported to debris sites and then to a refuse facility or dump at which the collected debris is off loaded. U.S. Pat. No. 5,030,259 discloses such an industrial vacuuming vehicle.
Industrial vacuum cleaning systems require a powerful vacuum and as a consequence are subject to certain occurrences which requires rapid cutoff of the suction at the intake end of the suction hose. One of these occurrences involves blockage of the inlet end by the debris being collected. Another occurrence involves the hazard of accidental sucking of some part of the body of clothing of the operator or other nearby person into the intake end of the suction hose.
To permit such rapid suction cutoff, it is known to provide the suction hose with a vacuum relief valve at a position close to the intake end of the hose. This valve normally remains closed during vacuuming operation so that all air flow into the hose occurs through its intake end. Opening the relief valve provides a relatively large air by-pass or vacuum relief inlet in the hose downstream of its intake end and thereby substantially reduces the suction at the intake end.
The prior vacuum relief valve has a generally T-shaped body including a tubular portion and a lateral portion between the ends of the tubular portion. A main flow passage extends axially through the tubular body portion. Extending axially through the lateral body portion is a vacuum relief passage which opens at one end to the main flow passage and at its other end to atmosphere. The tubular body portion has couplings at its ends for connecting the valve between two adjacent sections of a vacuum cleaning system hose so that during operation of the system, suction air and debris passes through the flow passage in the tubular body portion.
Journalled on the lateral body portion on an axis transverse to the vacuum relief passage is a spring loaded relief valve flapper situated within the relief passage and a trip lever situated externally of the valve body at one side of the lateral body portion. The relief valve flapper is normally latched closed to block air flow through the relief passage. The trip lever occupies a normal position when the valve flapper is closed and is rotatable in one direction on the transverse axis transverse from this normal position to release the flapper for opening. A tether line is secured at one end to the trip lever and has an opposite free end to be held by the vacuum operator. The operator may quickly open the relief valve at any time to cut off the suction at the intake end of the suction hose by pulling on the tether.
This prior relief valve suffers from the disadvantage that a pull on the tether will open the relief valve only if the direction of the tether relative to the valve when the tether is pulled is within a relatively narrow range of directions. This range of directions is that within which the pulling force exerted on the trip lever through the tether has at least a substantial force component which is (a) transverse to the lever, (b) in the plane of lever rotation, and (c) in the proper direction of lever rotation to open the valve. In the course of using a vacuum cleaning system, however, the operator generally moves about a wide area relative to the relief valve and in so doing, his position relative to the relief valve continuously changes. In many of these relative positions, the direction of the tether relative to the valve may be outside the range of directions necessary to open the valve. For example, if the operator's position when the tether is pulled is such that the tether extends transverse to the plane of rotation of the trip lever, or in a direction opposite to the direction of trip lever rotation necessary to open the valve, the tether pull will not open the valve. Accordingly, there is a need for an improved vacuum relief valve of the character described which avoids the above disadvantage.